Toll-like receptor 9 mediates paraquat-induced acute lung injury: an in vitro and in vivo study

AimsThis study aimed to investigate the role of Toll-like receptor 9 in paraquat-induced acute lung injury (ALI).Main methodsFor in vivo study,C57BL mice were randomly assigned into the vehicle control group, paraquat group, paraquat + TLR9 antagonist (ODN2088) group, and TLR9 antagonist (ODN2088) group (n = 36 per group). After paraquat 30 mg/kg ip for 2, 24 and 48 h, serum samples and lung tissues were collected to evaluate ALI and TLR9 signaling by lung injury score, protein levels of TLR9, MyD88, p-IRAK4, p-p65, and serum TNF-α and IL-1β levels. As for in vitro research A549 cells were randomly divided into the control group, paraquat group, paraquat + TLR9 siRNA group, and TLR9 siRNA group. After paraquat treatment for 24 h, the cells and supernatant were collected to measureTLR9, TNF-α, IL-1 mRNA expression, and detect activation of NF-κB, caspase-3.Key findingsIn vivo, the lung injury score, the TLR9, MyD88, p-IRAK4 and p-p65 protein levels, and cytokines TNF-α and IL-1β levels in paraquat group were significantly higher than that in the control group;TLR9 blocker ODN2088 pretreatment attenuated lung injury, inhibited MyD88 and NF-κB activation, and reduced TNF-α and IL-1β in serum. In vitro result shows that the gene silencing of TLR9 reduced the mRNA expression of TLR9, TNF-α and IL-1, inhibited NF-κB and caspase-3 activation, attenuated cell apoptosis.SignificanceTLR9 mediates paraquat-induced ALI, antagonizing TLR9 or silencing TLR9gene may attenuate paraquat-induced ALI.